The wealth of the United States has been created largely through the exploitation of cheap energy provided by the past abundance of fossil fuels. Because of the increasing shortages of natural gas in North America and the approaching worldwide shortages of oil, and because of the growing danger of global warming caused by the combustion of fossil fuels, reliable sources of renewable energy are needed.
A growing percentage of the efforts to utilize renewable sources of energy have been concentrated in the creation of wind farms. Although wind powered generating systems should be encouraged, they do have a problem: wind energy is inherently intermittent. Wind speeds can fluctuate hourly and have marked seasonal and diurnal patterns. They also frequently produce the most power when the demand for that power is at its lowest. This is known in the electricity trade as a low capacity factor. Low capacity factors, and still lower dependable on-peak capacity factors, are the major source of wind power's problem.
Because of the steadiness of the Coriolis force driven ocean currents, submersible generators can have capacity factors equal to those of many fossil fuel plants. The fact that these ocean currents can produce a steady supply of electricity makes that power much more valuable than the intermittent power produced by the wind-driven turbines. For submersible turbines to achieve high capacity factors, however, proper placement is very important.
Ocean currents flow at all depths in the ocean, but the strongest usually occur in the upper layer, which is shallow compared to the depth of the oceans. The main cause of surface currents in the open ocean is the action of the wind on the sea surface. A wind of high constancy, blowing over great stretches of an ocean, have the greatest effect on producing current. It is for this reason that the north-west and south-east trade winds of the two hemispheres are the mainspring of the oceans surface current circulation. In the Atlantic and Pacific oceans, the two trade winds drive an immense body of water westward over a width of some 50 degrees of latitude, broken only by the narrow belt of the east-going Equatorial Counter-current, which is found a few degrees north of the equator in both of these oceans. A similar westward flow of water occurs in the South Indian Ocean, driven by the south-east trade wind. These westward surface currents produce giant eddies that are centered in latitudes of approximately 30° N. and S. that rotate clockwise in the northern hemisphere and counter-clockwise in the southern hemisphere. Currents of over 3.5 mph are confined to very restricted regions. They have been recorded in the equatorial regions of the oceans, and in the warm currents flowing to higher latitudes in the western sides of the oceans, with the exception of the Brazil current. The book, Ocean Passages of the World (published by the Hydrographic Department of the British Admiralty, 1950), lists fourteen currents that exceed 3 knots (3.45 mph), a few of which are in the open ocean. The Gulf Stream and the Kuro Shio are the only two currents the book lists having velocities above 3 knots that flow throughout the year. Both of these currents are driven by the Coriolis force that is caused by the Earth's eastward rotation acting upon the ocean currents produced by the trade winds. Because these currents are caused by the Earth's rotation, they will continue flowing as long as our planet continues to turn on its axis.
The Gulf Stream starts roughly in the area where the Gulf of Mexico narrows to form a channel between Cuba and the Florida Keys. From there the current flows northeast through the Straits of Florida, between the mainland and the Bahamas, flowing at a substantial speed forsome 400 miles. It hits its peak velocity off Miami, where the Gulf Stream is about 45 miles wide and 1,500 feet deep. There the current reaches speeds of as much as 6.9 mph in its narrow central axis, which is located less than 18 miles from shore between Key Largo and North Palm Beach. Farther along it is joined by the Antilles Current, coming up &om the southeast, and the merging flow, broader and moving more slowly, continues northward and then northeastward, where it roughly parallels the 100-fathom curve as far as Cape Hatteras.
The Kuro Shio is the Pacific Ocean's equivalent to the Gulf Stream. A large part of the water of the North Equatorial current turns northeastward cast of Luzon and passes the cast coast of Taiwan to form this current. South of Japan, the Kuro Shio flows in a northeasterly direction, parallel to the Japanese islands, of Kyushu, Shikoku, and Honshu. According to Ocean Passages of the World, the top speed of the Kuro Shio is about the same as that of the Gulf Stream. The Gulf Stream's top flow rate is 156.5 statute miles per day (6.52 mph) and the Kuro Shio's is 153 statute miles per thy (6.375 mph). Other possible sites for the underwater generators are the East Australian Coast current, which flows at a top rate of 110.47 statute miles per day (4.6 mph), and the Agulhas current off the southern tip of South Africa, which flows at a top rate 01139.2 statute miles per day (5.8 mph). Another possible site for these generators is the Strait of Messina, the narrow opening that separates the island of Sicily from Italy, where the current's steady counter-clockwise rotation is produced—not by the wind—but by changing water densities produced by evaporation in the Mediterranean. Oceanographic current data will suggest other potential sites where such generators would be best placed. Therefore, there is a need for still further means of producing electricity in an efficient, non-fossil fuel manner yet which is usable in a variety of locations utilizing currents at the surface of the ocean.
Running water from rivers has long been used to power machinery and, more recently, to generate electricity. The majority, if not all, of the electricity produced by running water is produced by high efficiency hydroelectric power plants located in dams. Due to ecological, economical, and/or topological factors, there are relatively few sites that are suitable for dam construction. There are, however, numerous rivers that have sufficient current to produce sufficient quantities of electricity, if they can be properly tapped. There have been various proposals in the past to tap the energy available in river current without the use of dams. To the knowledge of the inventor of the present invention, none of these proposals has successfully put waterpower to use to produce energy in sufficient quantities. Therefore, there is a need for a means for producing electricity from the flow of water in a river that does not require that the river be dammed.
Finally, many states have passed laws requiring power companies to purchase surplus electricity from private generation facilities. As this is the case, there is an incentive for people who have the ability to generate power, such as those living on fast moving rivers, to install generation systems. However, the cost of such systems has, heretofore, been too high to justify such an investment. Therefore, there is a need for a relatively low cost power plant that may be installed by consumers living on fast moving rivers.
As can be seen from the foregoing, there is a need for means of producing electricity without the use of fossil fuels that is efficient, that is usable in a variety of locations, that may be adapted to utilize currents at the surface of the ocean, that may produce electricity from the flow of water in a river without requiring that the river be dammed, and that may be manufactured at a relatively low cost so as to allow it to be installed by consumers living on fast moving rivers.